Try Practice Questions

Read the following passage and answer the questions below

Sample Passage

Cystic fibrosis (CF) is the most common autosomal recessive disease in the Caucasian population. The disease affects 1 in 2500 newborns, and ranges in degree of severity even within the same family. In some cases, individuals do not survive past the age of five, while in others, adults live full lives through careful management.

It has been determined that CF is caused by a mutation of chromosome 7. In 75 percent of all CF cases, the mutation involves a deletion of three base pairs in a DNA sequence that codes for a transmembrane chloride channel. As a result of the deletion, the chloride channel is unable to operate efficiently.

CF is characterized by sticky, viscous, mucus secretions that impair the normal physiological functions of many organs, most especially the pancreas and lungs. Patients usually suffer from diarrhea, pancreatic exocrine insufficiency, and chronic obstructive pulmonary disease. Breathing is often difficult, and carbon dioxide tends to remain in the blood of CF patients longer than in that of healthy individuals.

The diarrhea and pancreatic troubles are treated with enzyme supplementation; the respiratory ailments prove more trying in their treatment. Patients must undergo intense, daily respiratory therapy, and take heavy doses of antibiotics in order to maintain adequate ventilation. One such antibiotic is cephalosporin C, which is effective against penicillin-resistant bacteria. Despite the rigorous treatments, individuals with CF usually die as a result of pneumonia or bacterial infections secondary to the respiratory aspects of the disease.

Sample Questions

1. One of the most common bacteria to infect patients with CF is Staphylococcus. If a sample from a CF patient were cultured, how would Staphylococcus appear when stained and viewed under a microscope?

A. Helical

B. Sickle-shaped

C. Rod-like

D. Spherical

2. According to the passage, pancreatic insufficiency in CF patients can be effectively treated with enzyme supplementation. Which of the following substances is LEAST likely to be found in such a supplement?

A. Lipase

B. Trypsin

C. Enterokinase

D. Chymotrypsinogen

3. What is the probability that a child of two carriers of the CF gene will be affected with CF?

A. 0 percent

B. 25 percent

C. 50 percent

D. 66 percent